Detectors D for locating particles are known, such as that illustrated in FIG. 1 comprising a gas enclosure 1 that is filled with an appropriate gaseous mixture, such a detector D enabling the amplification of electrons by an avalanche process. Such a detector is particularly disclosed by the document FR2786024. In this particular case, the particles are photons.
The gaseous mixture contained in the enclosure 1 may remain confined in the enclosure 1 or circulate through a purifier (not illustrated) through pipes 2.
This enclosure 1 is closed in a sealed manner by a window 3 transparent to the photons 4 to be detected. The detector D also comprises an electrically insulating plate 5 of very good flatness, on which is formed the active part of the detector D, in particular elementary anodes 6 which may be parallel metal tracks or metal elements that may be referred to as “pixels” and which form a two-dimensional network on the electrically insulating plate 5. The set of tracks constitutes the anode 7 of the detector D. The tracks are earthed and are connected to suitable electronic means 8 provided for amplifying then processing the electrical signals coming from these tracks.
Moreover, this active part comprises, facing the window 3, a cathode 9 constituted of a metal sheet pierced with holes 10, said sheet thereby forming a grid. The anode 7 and the grid 9 are maintained parallel to each other by means of electrically insulating spacers 11 that rest on the anode 7.
Polarisation means 12 are moreover provided to take the grid 9 (in other words the cathode) to a highly negative voltage compared to the anode 7 (this voltage depending on the gaseous mixture used). The anode 7, which is thus taken to a high potential compared to the cathode 9, constitutes with the latter a detector with parallel electrodes capable of amplifying electrons by an avalanche process that develops between these electrodes. In the example represented, the high voltage is chosen to create in the space A comprised between the anode 7 and the cathode 9, or amplification space, an electric field EA of which the intensity is greater than or equal to 50 kV/cm.
In the case of the detection of non-ionising particles such as photons, it is necessary to add a conversion layer 13 to convert the non-ionising particles into ionising particles.
This type of particle detector nevertheless has drawbacks. In fact, when it is desirable to obtain a curved structure, it is necessary to join up end to end a plurality of flat structures so as to obtain a curved surface. This particularity does not make it possible in any case to obtain a compact or even light detector.